Returns the Vandermonde matrix of degree deg and sample points
x. The Vandermonde matrix is defined by

where 0 <= i <= deg. The leading indices of V index the elements of
x and the last index is the power of x.

If c is a 1-D array of coefficients of length n + 1 and V is the
matrix V=polyvander(x,n), then np.dot(V,c) and
polyval(x,c) are the same up to roundoff. This equivalence is
useful both for least squares fitting and for the evaluation of a large
number of polynomials of the same degree and sample points.

Parameters:

x:array_like

Array of points. The dtype is converted to float64 or complex128
depending on whether any of the elements are complex. If x is
scalar it is converted to a 1-D array.

deg:int

Degree of the resulting matrix.

Returns:

vander:ndarray.

The Vandermonde matrix. The shape of the returned matrix is
x.shape+(deg+1,), where the last index is the power of x.
The dtype will be the same as the converted x.